Sunan an-Nasa'i 2185

It was narrated that 'Abdullah bin Shaqiq said:'I said to Aishah: 'did the Messenger of Allah offer Duah prayer?' she said: 'No, unless he was returning from a journey.' I said: 'was the Messenger of Allah known to observe any fast regularly apart from Ramadan?'' She said: 'by Allah, he did not observe any fast regularly apart from amadan until he passed away, and he did not break his fast for a whole month, rather he would fast some of it (each month)